A wire or a cable used in electrical and electronic parts requires various properties including flame retardant properties, physical properties after thermal deterioration, properties at a low temperature, heat resistance, etc., particularly, flame retardant properties satisfying the high degree of retardancy grade (VW-1) based on UL-1581 with North American countries as the center.
In the present, an economical material including PVC or a halogen retardant agent, satisfying all the above-described conditions is generally used as a material for coating. However, for the PVC, toxic gases threatening a human body and natural environment, such as hydrochloride, dioxin may be generated in the event of fire or during performing an incinerating process after use. Thus, the regulation on the use of the PVC is under discussion with developed countries in Europe, America, Japan, etc., as the center. In addition, for other resins including the halogen flame retardant agent, since a hydrogen halide harmful to a human body and natural environment is generated, there are also restrictions on the use thereof.
Recently, as a non-halogen coating material of a wire, capable of improving the defects, a composition having a polyolefin-based resin as a base and including a metal hydroxide such as magnesium hydroxide and aluminum hydroxide has been suggested. However, since an excessive amount of the metal hydroxide is necessary to exhibit flame retardant properties, the deterioration of the physical properties of the composition including the lowering of the flexibility or the tensile strength of the wire may be generated. In addition, the metal hydroxide in a powder state and various additives including a flame retardant agent in a powder state may stick to each other, and the insertion thereof may become difficult.
As another method, a method of imparting flame retardant properties by using a polyphenylene oxide with an elastomer and a phosphor-based flame retardant agent has been suggested. However, polyphenylene oxide forms char to produce a solid blocking layer and the system thus produced blocks heat and oxygen, however the elastomer alone could not exhibit flame retardant properties.
Particularly, since the polyphenylene oxide does not have flexible properties, in the case that the amount of the polyphenylene oxide is increased to attain flame retardant properties; various physical properties required for a resin for coating a wire such as flexibility may be deteriorated.
Therefore, the development of a flexible and eco-friendly flame retardant resin composition is necessary to satisfy the flame retardancy grade on the basis of UL-1581.